Physicists at Glasgow University have found a way to make sophisticated but low-cost to produce 3D images without using conventional digital cameras. Their system uses simple, cheap detectors which use a single pixel — instead of the millions — to sense light. These detectors can sense frequencies beyond visible light, potentially opening up new uses for 3D imaging in medicine and industry. For example, the researchers suggest that the technique could be used to locate oil or help doctors find tumours.
Prof Miles Padgett who led the team at the University’s School of Physics and Astronomy, explained that “single-pixel detectors in four different locations are used to detect light from a data projector, which illuminates objects with a rapidly-shifing sequence of black-and-white patterns similar to crossword puzzles. When more of the white squares of these patterns overlap with the object, the intensity of the light reflected back to the detectors is higher. A series of projected patterns and the reflected intensities are used in a computer algorithm to produce a 2D image.”
He added that a 3D image was then created by combining images from the four detectors using a well-known technique called “shape from shade”. This method known as “ghost imaging” produces detailed images of objects in just a few seconds. Contrast this with conventional 3D imaging systems which use several camera sensors to produce a 3D image from 2D information. It means that careful calibration is needed to make sure the many images are correctly aligned.
As the Professor pointed out, “Our single-pixel system creates images with a similar degree of accuracy without the need for such detailed calibration.”
Lead author on the paper Baoqing Sun described the process as being “a bit counter-intuitive to think that more information can be captured from a detector which uses just a single pixel rather than the multi-megapixel detectors found in conventional digital cameras. However, digital camera sensors have a very limited sensitivity beyond the spectrum of visible light, whereas a single-pixel detector can easily be made to capture information far beyond the visible, reaching wavelengths from X-ray to TeraHertz.”
The team’s paper, 3D Computational Imaging with Single-Pixel Detectors, is published in the journal, Science.